/Engine/Source/Runtime/Core/Public/Async/AsyncFileHandle.h
Transfer ownership of Memory from the async request to the outside caller (called in response to GetReadResults). It's only relevant to Read requests, in which case the most common use is to update (decrease) the STAT_AsyncFileMemory stat which is typically incremented when async requests allocate Memory. It doesn't play any role in Size requests, so it may be left empty for them.
void ReleaseMemoryOwnershipImpl()